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VIMS Articles

2002

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Full-Text Articles in Life Sciences

Biodiversity And Ecosystem Function: The Consumer Connection, J. Emmett Duffy Dec 2002

Biodiversity And Ecosystem Function: The Consumer Connection, J. Emmett Duffy

VIMS Articles

Proposed links between biodiversity and ecosystem processes have generated intense interest and controversy in recent years. With few exceptions, however, empirical studies have focused on grassland plants and laboratory aquatic microbial systems, whereas there has been little attention to how changing animal diversity may influence ecosystem processes. Meanwhile, a separate research tradition has demonstrated strong top‐down forcing in many systems, but has considered the role of diversity in these processes only tangentially. Integration of these research directions is necessary for more complete understanding in both areas. Several considerations suggest that changing diversity in multi‐level food webs can have ...


Long-Distance Dispersal Potential In A Marine Macrophyte, Mc Harwell, R J. Orth Dec 2002

Long-Distance Dispersal Potential In A Marine Macrophyte, Mc Harwell, R J. Orth

VIMS Articles

Plant populations have long been noted to migrate faster than predicted based on their life history and seed dispersal characteristics (i.e., Reid's paradox of rapid plant migration). Although precise mechanisms to account for such phenomena are not fully known for all plant species, a combination of theoretical and empirically driven mechanisms often resolves this paradox. Here, we couple a series of direct and indirect field and laboratory exercises on one marine macrophyte, Zostera marina L. (eelgrass), to measured distances between new patches and established beds in order to elucidate the longdistance dispersal and colonization potential of this marine ...


Continuous In Vitro Culture Of The Carpet Shell Clam Tapes Decussatus Protozoan Parasite Perkinsus Atlanticus, Sm Casas, Jf La Peyre, Kimberly S. Reece, C Azevedo, A Villalba Dec 2002

Continuous In Vitro Culture Of The Carpet Shell Clam Tapes Decussatus Protozoan Parasite Perkinsus Atlanticus, Sm Casas, Jf La Peyre, Kimberly S. Reece, C Azevedo, A Villalba

VIMS Articles

Continuous in vitro cultures of the clam Tapes decussatus parasite Perkinsus atlanticus were established from infected gill fragments, infected haemolymph and parasite hypnospores isolated from infected gill fragments following incubation in Ray's fluid thioglycollate medium (RFTM). No continuous cultures could be initiated from P. atlanticus zoospores. Cultures initiated from hypnospores yielded the highest percentage of continuous cultures (100%, 6/6), followed by cultures initiated from gill fragments (93%, 43/46) and from haemolymph (30%, 3/10). Failures to establish continuous cultures were due to microbial contamination, The source of parasite influenced the success rate, the time taken to establish ...


The Magnitude Of Spring Bacterial Production In The North Atlantic Ocean, Hw Ducklow, Dl Kirchman, Tr Anderson Nov 2002

The Magnitude Of Spring Bacterial Production In The North Atlantic Ocean, Hw Ducklow, Dl Kirchman, Tr Anderson

VIMS Articles

Dissolved organic carbon (DOC), a major reservoir in the ocean carbon cycle, is produced by a profusion of plankton sources and processes but is consumed mainly by bacterioplankton. Thus bacterial metabolism regulates the entry of DOC into the longer scale global carbon cycle. Bacterial production (BP) is the routinely measured quantity for evaluating the roles of bacteria in carbon cycling. However BP cannot be measured directly and instead is estimated from related metabolic processes requiring the use of poorly constrained conversion factors. BP and thus the total carbon utilization, are potentially uncertain by a factor of two or more. In ...


A Perspective On Two Decades Of Policies And Regulations Influencing The Protection And Restoration Of Submerged Aquatic Vegetation In Chesapeake Bay, Usa, R J. Orth, Ra Batiuk, Pw Bergstrom, Ken Moore Nov 2002

A Perspective On Two Decades Of Policies And Regulations Influencing The Protection And Restoration Of Submerged Aquatic Vegetation In Chesapeake Bay, Usa, R J. Orth, Ra Batiuk, Pw Bergstrom, Ken Moore

VIMS Articles

Seagrasses along with many other species of freshwater rooted submerged macrophytes in Chesapeake Bay (collectively called SAV) underwent serious declines in population abundances in the 1970s and have not as yet rebounded to previous levels. Cooperative efforts by scientists, politicians, federal and state resource managers, and the general public have developed policies and plans to protect, preserve and enhance SAV populations of Chesapeake Bay. These include the Chesapeake Bay Agreements (1983, 1987, 1992, 1993, 2000), an SAV Management Policy and Implementation Plan for Chesapeake Bay and Tidal Tributaries (1989 and 1990), Chesapeake Bay Blue Crab Fishery Management Plan (1997), as ...


Molecular Diagnostics, Field Validation, And Phylogenetic Analysis Of Quahog Parasite Unknown (Qpx), A Pathogen Of The Hard Clam Mercenaria Mercenaria, Na Stokes, Lm Ragone Calvo, Kimberly S. Reece, Em Burreson Oct 2002

Molecular Diagnostics, Field Validation, And Phylogenetic Analysis Of Quahog Parasite Unknown (Qpx), A Pathogen Of The Hard Clam Mercenaria Mercenaria, Na Stokes, Lm Ragone Calvo, Kimberly S. Reece, Em Burreson

VIMS Articles

Quahog Parasite Unknown (QPX) is a protistan parasite that causes disease and mortality in the hard clam Mercenaria mercenaria. PCR primers and DNA oligonucleotide probes were designed and evaluated for sensitivity and specificity for the QPX organism specifically and for the phylum Labyrinthulomycota in general. The best performing QPX-specific primer pair amplified a 665 bp region of the QPX small-subunit ribosomal DNA (SSU rDNA) and detected as little as 1 fg cloned QPX SSU rDNA and 20 fg QPX genomic DNA. The primers did not amplify DNA of uninfected hard clams M. mercenaria or of the thraustochytrids Schizochytrium aggregatum, Thraustochytrium ...


Relative Strengths Of Competition For Space And Food In A Sessile Filter Feeder, David P. Lohse Oct 2002

Relative Strengths Of Competition For Space And Food In A Sessile Filter Feeder, David P. Lohse

VIMS Articles

Previous workers have demonstrated that sessile filter feeders compete for food and space, but little is known about the relative strengths of these two processes. To determine this, the density and position of barnacles (Balanus improvisus) in a unidirectional current were manipulated to alter the amount of competition for space and food, respectively. Results indicated that competition for space significantly reduced growth, and marginally reduced survivorship. Competition for food was also detected, but only among uncrowded individuals; thus, it appears to be the weaker of the two interactions. However, under crowded conditions, downstream individuals actually grew more than those upstream ...


The Microbial And Metazoan Community Associated With Colonies Of Trichodesmium Spp.: A Quantitative Survey, Cc Sheridan, Deborah K. Steinberg, Gw Kling Sep 2002

The Microbial And Metazoan Community Associated With Colonies Of Trichodesmium Spp.: A Quantitative Survey, Cc Sheridan, Deborah K. Steinberg, Gw Kling

VIMS Articles

Association with resource-rich particles may benefit a number of planktonic species in oligotriphic, open-ocean regimes. This study examined communities of microbes and Zooplankton associated with colonies of the cyanobacterium Trichodesmium spp. in the Sargasso Sea. Trichodesmium colonies and seawater controls were collected near Bermuda using SCUBA during September 1995, and June, July and August 1996. Organisms associated with the colonies and those in the surrounding seawater were enumerated using light and fluorescence microscopy. We found that 85% of the Trichodesmium puff and tuft colonies examined harbored associated organisms. Associated organisms included bacteria (rod and coccoid),fungi, pennate diatoms, centric diatoms ...


Are Pfiesteria Species Toxicogenic? Evidence Against Production Of Ichthyotoxins By Pfiesteria Shumwayae, Jp Berry, Kimberly S. Reece, Ks Rein, Dg Baden, Lw Haas, Wl Ribeiro, Jeffrey D. Shields, Rv Snyder, Wolfgang K. Vogelbein, Re Gawley Aug 2002

Are Pfiesteria Species Toxicogenic? Evidence Against Production Of Ichthyotoxins By Pfiesteria Shumwayae, Jp Berry, Kimberly S. Reece, Ks Rein, Dg Baden, Lw Haas, Wl Ribeiro, Jeffrey D. Shields, Rv Snyder, Wolfgang K. Vogelbein, Re Gawley

VIMS Articles

The estuarine genus Pfiesteria has received considerable attention since it was first identified and proposed to be the causative agent of fish kills along the mid-Atlantic coast in 1992. The presumption has been that the mechanism of fish death is by release of one or more toxins by the dinoflagellate. In this report, we challenge the notion that Pfiesteria species produce ichthyotoxins. Specifically, we show that (i) simple centrifugation, with and without ultrasonication, is sufficient to "detoxify" water of actively fish-killing cultures of Pfiesteria shumwayae, (ii) organic extracts of lyophilized cultures are not toxic to fish, (fit) degenerate primers that ...


Nuclear And Mitochondrial Dna Markers For Specific Identification Of Istiophorid And Xiphiid Billfishes, Jan Mcdowell, John Graves Jul 2002

Nuclear And Mitochondrial Dna Markers For Specific Identification Of Istiophorid And Xiphiid Billfishes, Jan Mcdowell, John Graves

VIMS Articles

Independent molecular markers based on mitochondrial and nuclear DNA were developed to provide positive identification of istiophorid and xiphiid billfishes (marlins, spearfishes, sailfish, and swordfish). Both classes of markers were based on amplification of short segments (


Two Epizootic Diseases In Chesapeake Bay Commercial Clams, Mya Arenaria And Tagelus Plebeius, Cf Dungan, Rm Hamilton, Kl Hudson, Cb Mccollough, Kimberly S. Reece Jun 2002

Two Epizootic Diseases In Chesapeake Bay Commercial Clams, Mya Arenaria And Tagelus Plebeius, Cf Dungan, Rm Hamilton, Kl Hudson, Cb Mccollough, Kimberly S. Reece

VIMS Articles

Declining Chesapeake Bay harvests of softshell clams, together with historical and emerging reports of epizootic diseases in Mya arenaria, prompted a survey in summer 2000 of the health status of selected commercial clam populations. All sampled populations (8 M. arenaria softshell clam, 2 Tagelus plebeius razor clam) were infected by Perkinsus sp. protozoans at prevalences ranging from 30 to 100% of sampled clams. Nucleotide sequences for the internal transcribed spacer (ITS) region of the rRNA gene complex were determined for clonal in vitro Perkinsus sp. isolates propagated from both M arenaria and T plebeius. Multiple polymorphic sequences were amplified from ...


Study Of Perkinsosis In The Carpet Shell Clam Tapes Decussatus In Galicia (Nw Spain). I. Identification Of The Aetiological Agent And In Vitro Modulation Of Zoosporulation By Temperature And Salinity, Sm Casas, A Villalba, Kimberly S. Reece Jun 2002

Study Of Perkinsosis In The Carpet Shell Clam Tapes Decussatus In Galicia (Nw Spain). I. Identification Of The Aetiological Agent And In Vitro Modulation Of Zoosporulation By Temperature And Salinity, Sm Casas, A Villalba, Kimberly S. Reece

VIMS Articles

Morphological characters of zoosporulation stages and DNA sequence of the internal transcribed spacer (ITS) region and the small subunit ribosomal RNA (SSU rRNA) gene confirmed that the aetiological agent of perkinsosis in the clam Tapes decussatus from Galicia (NW Spain) was Perkinsus atlanticus Azevedo, 1989. In vitro modulation by temperature and salinity of the zoosporulation of the parasite was studied. The optimum temperature range for zoosporulation was 19 to 28degreesC. The temperature range allowing zoosporulation in vitro was 15 to 32degreesC, which is broader than previously reported (24 to 28degreesC) for R atlanticus, and strongly suggests that zoospores can be ...


Observations On The Distribution Of Meroplankton During A Downwelling Event And Associated Intrusion Of The Chesapeake Bay Estuarine Plume, Al Shanks, J Largier, L Brink, J Brubaker, R Hooff Apr 2002

Observations On The Distribution Of Meroplankton During A Downwelling Event And Associated Intrusion Of The Chesapeake Bay Estuarine Plume, Al Shanks, J Largier, L Brink, J Brubaker, R Hooff

VIMS Articles

We investigated the dispersal of larvae of benthic invertebrates and tested the hypothesis that larvae behaved as if they were passive particles. Observations were made off Duck, North Carolina, USA diving a period of wind driven downwelling at the coast and an intrusion of estuarine water from the Chesapeake Bay. The plume of estuarine water (salinity < 30 psu) was strongest at the shoreward stations in the more northern transects. Wind driven shoreward surface flow, converged at the seaward edge of the plume and downwelled. Offshore flow was present below the thermocline and caused the thermocline to bend downward and contact the bottom at between 5 and 10 km offshore. In the zooplankton samples, we enumerated 33 taxa of larvae (17 taxa of bivalve veligers, 10 taxa of gastropod veligers, and 6 taxa of polychaete larvae). Using cluster analysis, larvae were separated into groups with similar patterns of distribution. If larvae were acting as passive particles then we hypothesized that: 1) Their distribution should remain tied to a water mass and 2) around a convergence or divergence, there should be no change in larval concentration. The distributions of larvae in Clusters 1, 4, 5, and 6 were consistent with the hypothesis that thy were acting as passive particles. Larvae in Clusters 2 and 3, however, did not appear to be acting as passive particles. Larvae in Cluster 2 did not remain tied to a water mass. They entered the study area in the estuarine plume waters, but within 20 km they were nearly absent from the plume water and were found seaward of the plume and at greater depth. Larvae in Cluster 3 were most abundant in areas of converging currents where the shoreward flowing surface waters downwelled at the plume front or against the shore. We hypothesized that larvae of organisms which as adults live in the intertidal or shallow, subtidal zones would have more nearshore distributions than the larvae of adults that are broadly distributed across the shelf. We compared the depth of the habitat of the adult bivalves from which the bivalve larvae in the different clusters were derived. The results were consistent with the hypothesis; larvae with distributions closer to shore tended to come from adults found at shallower depths or in the intertidal zone.


Widespread Distribution In Polar Oceans Of A 16s Rrna Gene Sequence With Affinity To Nitrosospira-Like Ammonia-Oxidizing Bacteria, Jt Hollibaugh, Hw Ducklow, N Bano Mar 2002

Widespread Distribution In Polar Oceans Of A 16s Rrna Gene Sequence With Affinity To Nitrosospira-Like Ammonia-Oxidizing Bacteria, Jt Hollibaugh, Hw Ducklow, N Bano

VIMS Articles

We analyzed the phylogenetic compositions of ammonia-oxidizing bacteria of the beta subclass of Proteobacteria from 42 Southern Ocean samples. We found a Nitrosospira-like 16S rRNA gene sequence in all 20 samples that yielded PCR products (8 of 30 samples from the Ross Sea and 12 of 12 samples from the Palmer Peninsula). We also found this sequence in Arctic Ocean samples, indicating a transpolar, if not global, distribution; however, slight differences between Arctic and Antarctic sequences may be evidence of polar endemism.


Haplosporidium Costale (Seaside Organism), A Parasite Of The Eastern Oyster, Is Present In Long Island Sound, I Sunila, Na Stokes, R Smolowitz, Rc Karney, E. M. Burreson Jan 2002

Haplosporidium Costale (Seaside Organism), A Parasite Of The Eastern Oyster, Is Present In Long Island Sound, I Sunila, Na Stokes, R Smolowitz, Rc Karney, E. M. Burreson

VIMS Articles

A haplosporidian parasite, Haplosporidium costale (seaside organism or SSO), is associated with high mortalities of eastern oysters (Crassostrea virginica) in seaside bays of Virginia and Maryland. Its presence in Long Island Sound has been tentatively suggested in several publications for the last 50 y. Positive identification of H. costale and differentiation from another haplosporidian parasite, Haplosporidium nelsoni (MSX), from histological sections is difficult and requires the presence of spores. We detected H. costale spores in 4 out of 5010 (0.08%) oysters collected from Long Island Sound in 1997-1999. In situ hybridization using an oligonucleotide DNA probe designed to detect ...


Hybridization Of Tetraploid And Diploid Crassostrea Gigas (Thunberg) With Diploid C-Ariakensis (Fujita), H Que, Standish K. Allen Jr. Jan 2002

Hybridization Of Tetraploid And Diploid Crassostrea Gigas (Thunberg) With Diploid C-Ariakensis (Fujita), H Que, Standish K. Allen Jr.

VIMS Articles

Three replicates of hybrid crosses of tetraploid and diploid C gigas (Thunberg) with diploid C ariakensis (Fujita) were produced with controls. Larval survival and growth were documented. Cytological events were also monitored in oocytes from hybrid crosses following insemination. Among the four types of hybrid crosses, diploid C. gigas (female) x diploid C. ariakensis (male) (GA) was the most successful. Survival of GA was about the same as that of controls in two of three replications, although its growth rate was 25-30% lower. Crosses of tetraploid C. gigas (female) and diploid C. ariakensis (male) (GGA) had poor yield at day ...


Age And Growth Of The Smooth Dogfish (Mustelus Canis) In The Northwest Atlantic Ocean, Christina L. Conrath, J Gelsleichter, John A. Musick Jan 2002

Age And Growth Of The Smooth Dogfish (Mustelus Canis) In The Northwest Atlantic Ocean, Christina L. Conrath, J Gelsleichter, John A. Musick

VIMS Articles

The northwest Atlantic population of smooth dogfish (Mustelus canis) ranges from Cape Cod, Massachusetts, to South Carolina. Although M. canis is seasonally abundant in this region, very little is known about important aspects of its biology, such as growth and reproductive rates. In the early 1990s, commercial fishery landings of smooth dogfish dramatically increased on the east coast of the United States. This study investigated growth rates of the east coast M. canis population through analysis of growth patterns in vertebral centra. Marginal increment analysis, estimates of precision, and patterns in seasonal growth supported the use of vertebrae to age ...


Horizontal And Vertical Movements Of Juvenile Bluefin Tuna (Thunnus Thynnus), In Relation To Oceanographic Conditions Of The Western North Atlantic, Determined With Ultrasonic Telemetry, Richard Brill, Molly Lutcavage, Greg Metzger, Peter Bushnell, Michael D. Arendt, Jon Lucy, Cheryl Watson, David Foley Jan 2002

Horizontal And Vertical Movements Of Juvenile Bluefin Tuna (Thunnus Thynnus), In Relation To Oceanographic Conditions Of The Western North Atlantic, Determined With Ultrasonic Telemetry, Richard Brill, Molly Lutcavage, Greg Metzger, Peter Bushnell, Michael D. Arendt, Jon Lucy, Cheryl Watson, David Foley

VIMS Articles

We employed ultrasonic transmitters to follow (for up to 48 h) the horizontal and vertical movements of five juvenile (6.8-18.7 kg estimated body mass) bluefin tuna (Thunnus thynnus) in the western North Atlantic (off the eastern shore of Virginia). Our objective was to document the fishes' behavior and distribution in relation to oceanographic conditions and thus begin to address issues that currently limit population assessments based on aerial surveys. Estimation of the trends in adult and juvenile Atlantic bluefin tuna abundance by aerial surveys, and other fishery-independent measures, is considered a priority. Juvenile bluefin tuna spent the majority ...


An Evaluation Of Pop-Up Satellite Tags For Estimating Postrelease Survival Of Blue Marlin (Makaira Nigricans) From A Recreational Fishery, John Graves, Brian E. Luckhurst, Eric D. Prince Jan 2002

An Evaluation Of Pop-Up Satellite Tags For Estimating Postrelease Survival Of Blue Marlin (Makaira Nigricans) From A Recreational Fishery, John Graves, Brian E. Luckhurst, Eric D. Prince

VIMS Articles

No abstract provided.


Predation On Seeds Of The Seagrass Posidonia Australis In Western Australia, R J. Orth, Kl Heck, Dj Tunbridge Jan 2002

Predation On Seeds Of The Seagrass Posidonia Australis In Western Australia, R J. Orth, Kl Heck, Dj Tunbridge

VIMS Articles

Despite much evidence that predation governs seed abundance, and ultimately seedling and adult plant distribution and abundance in terrestrial ecosystems, there is a dearth of information from seagrass dominated ecosystems. We report here on the first study to examine predation rates from seeds of Posidonia australis measured during field tethering experiments at 5 locations in Western Australia. Seeds that were recently dehisced from ripe fruits and at a similar stage of development were tethered in seagrass and adjacent unvegetated sand for 24 h and then assessed for damage. Seed predation was noted at all sites and ranged from partially to ...


Habitat Quality And Prey Size As Determinants Of Survival In Post-Larval And Early Juvenile Instars Of The Blue Crab Callinectes Sapidus, R J. Orth, J Van Montfrans Jan 2002

Habitat Quality And Prey Size As Determinants Of Survival In Post-Larval And Early Juvenile Instars Of The Blue Crab Callinectes Sapidus, R J. Orth, J Van Montfrans

VIMS Articles

Habitat structure and prey size are important determinants in the outcome of predator-prey interactions. We investigated the role of simulated habitat type and density (simulated Zostera marina [hereafter referred to as 'Zostera']: 500 and 1500 shoots m(-2), and simulated Spartina alterniflora [hereafter referred to as 'Spartina']: 97 and 291 shoots m(-2)) in mediating predator-prey interactions. Proportional survival during predation by the piscene predator Fundulus heteroclitus on 2 successive life-history stages (post-larvae and first juvenile instars) of the blue crab Callinectes sapidus (Rathbun), was quantified under laboratory conditions that closely approximated field conditions. We also examined the effects of ...


Ecosystem Modeling Analysis Of Size-Structured Phytoplankton Dynamics In The York River Estuary, Virginia (Usa). Ii. Use Of A Plankton Ecosystem Model For Investigating Controlling Factors On Phytoplankton And Nutrient Dynamics, Y Sin, Rl Wetzel Jan 2002

Ecosystem Modeling Analysis Of Size-Structured Phytoplankton Dynamics In The York River Estuary, Virginia (Usa). Ii. Use Of A Plankton Ecosystem Model For Investigating Controlling Factors On Phytoplankton And Nutrient Dynamics, Y Sin, Rl Wetzel

VIMS Articles

An ecosystem simulation model was used to investigate potential mechanisms controlling the size-structured phytoplankton and nutrient dynamics in the mesohaline zone of the York River estuary, The York River ecosystem model (Sin & Wetzel 2001, Mar Ecol Prog Ser 228:75-90)was calibrated and validated based on field observations and laboratory measurements prior to the exercises reported here. Analyses of model sensitivity to state variable changes and parameter variations were performed to examine hypotheses proposed from previous studies regarding controls on phytoplankton and nutrient dynamics in the York River estuary. The model results supported the general view that phytoplankton dynamics may ...


Total Cover And Cover Quality: Predicted And Actual Effects On A Predator's Foraging Success, A Bartholomew Jan 2002

Total Cover And Cover Quality: Predicted And Actual Effects On A Predator's Foraging Success, A Bartholomew

VIMS Articles

I tested the importance of both total cover and cover quality to the foraging ability of large Fundulus heteroclitus fish in tanks. Total cover was measured as the combined areas of all the individual structures, viewed as shadows. I divided total cover by the bottom area of the tank to form C-t/A(t), an index that measures the total amount of structure available in a given area for prey to hide behind. Cover quality was measured as the width of each individual structure divided by the width of the individual prey organism (C-w/P-w). This index measures how visible ...


Concurrent Decline Of The Spawning Stock, Recruitment, Larval Abundance, And Size Of The Blue Crab Callinectes Sapidus In Chesapeake Bay, Rom Lipcius, Wt Stockhausen Jan 2002

Concurrent Decline Of The Spawning Stock, Recruitment, Larval Abundance, And Size Of The Blue Crab Callinectes Sapidus In Chesapeake Bay, Rom Lipcius, Wt Stockhausen

VIMS Articles

Conservation of exploited marine populations requires knowledge of interannual variation in the characteristics of and relationships between the spawning stock and recruitment, which determine Population resilience and persistence. We examined relationships between spawning stock abundance, postlarval recruitment, larval abundance, and female size of the blue crab in Chesapeake Bay, both within the Spawning grounds over a 13 yr interval (1988 to 2000) and within lower-bay tributaries over 20 yr (1979 to 1998). Our findings establish that there has been a concurrent, persistent and substantial reduction in the spawning stock, recruitment, larval abundance, and female size, Specifically, in 1992 to 2000 ...


Distribution Of The Euryhaline Squid Lolliguncula Brevis In Chesapeake Bay: Effects Of Selected Abiotic Factors, Ik Bartol, Roger L. Mann, M Vecchione Jan 2002

Distribution Of The Euryhaline Squid Lolliguncula Brevis In Chesapeake Bay: Effects Of Selected Abiotic Factors, Ik Bartol, Roger L. Mann, M Vecchione

VIMS Articles

The majority of cephalopods are thought to have limitations arising from physiology and locomotion that exclude them from shallow, highly variable, euryhaline environments. The brief squid Lolliguncula brevis may be a notable exception because it tolerates low salinities, withstands a wide range of environmental conditions, and swims readily in shallow water. Little is known about the distribution of L. brevis in Chesapeake Bay, a diverse and highly variable estuary. Therefore, a survey of L. brevis was conducted in the Virginia portion of Chesapeake Bay from 1993 to 1997 using a 9.1 m otter trawl, and the effects of selected ...


Across-Shelf Sediment Transport: Interactions Between Suspended Sediment And Bed Sediment, Courtney K. Harris, Patricia Wiberg Jan 2002

Across-Shelf Sediment Transport: Interactions Between Suspended Sediment And Bed Sediment, Courtney K. Harris, Patricia Wiberg

VIMS Articles

[1] We use a two-dimensional, time-dependent sediment-transport model to quantify across-shelf transport, deposition, and sorting during wave-driven resuspension events characteristic of those that dominate sediment transport on many continental shelves. Decreases in wave-orbital velocities as water depth increases, and the resulting cross-shelf gradient in bed shear stress favor a net offshore transport of sediment. On wide, flat shelves (slopes similar to0.1%), these gradients are low, and the depth to which the seabed is reworked depends mainly on bottom shear stress and local sediment availability. On narrow, steep shelves (slopes similar to0.5%), however, the gradient in bottom stress generates ...


Photochemical Production Of Dissolved Inorganic Nitrogen And Primary Amines From Dissolved Organic Nitrogen In Waters Of Two Estuaries And Adjacent Surficial Groundwaters, Dj Koopmans, Da Bronk Jan 2002

Photochemical Production Of Dissolved Inorganic Nitrogen And Primary Amines From Dissolved Organic Nitrogen In Waters Of Two Estuaries And Adjacent Surficial Groundwaters, Dj Koopmans, Da Bronk

VIMS Articles

Recent studies have shown that in a number of humic-rich surface waters in North America, NH4+ is released when dissolved organic matter (DOM) is exposed to sunlight. However, photochemical NH4+ production has not been observed in all surface waters, and factors that contribute to it are not well understood. We hypothesized that the presence or absence of NH4+ photoproduction may be affected by the light exposure history of DOM, The present study was undertaken to determine whether DOM from surficial groundwaters, with minimal light exposure history, would produce labile nitrogen (N) photoproducts more consistently, In this study, estuarine surface waters ...


Photo Synthesis/Irradiance Relationships In The Ross Sea, Antarctica, And Their Control By Phytoplankton Assemblage Composition And Environmental Factors, C. M. Van Hilst, Walker O. Smith Jr. Jan 2002

Photo Synthesis/Irradiance Relationships In The Ross Sea, Antarctica, And Their Control By Phytoplankton Assemblage Composition And Environmental Factors, C. M. Van Hilst, Walker O. Smith Jr.

VIMS Articles

The photosynthetic parameters of natural phytoplankton assemblages from the Ross Sea, Antarctica, as well as unialgal cultures of the diatom Pseudonitzschia sp. and the colonial haptophyte Phaeocystis antarctica were investigated to determine if differential responses to irradiance could explain the distribution of phytoplankton in the Ross Sea. Field assemblages had photosynthetic responses that suggested acclimation to low irradiance levels, and the initial rate of photosynthesis per unit chlorophyll (a) and the theoretical maximum rate of production (p(max)(B)) averaged 0,083 mg C (mg chl a)(-1) h(-1) (mumol m(-2) s(-1))(-1) and 2,40 mg ...


Assimilating High-Resolution Salinity Data Into A Model Of A Partially Mixed Estuary, Jiangtao Xu, Shenn-Yu Chao, Raleigh R. Hood, Harry V. Wang Jan 2002

Assimilating High-Resolution Salinity Data Into A Model Of A Partially Mixed Estuary, Jiangtao Xu, Shenn-Yu Chao, Raleigh R. Hood, Harry V. Wang

VIMS Articles

[1] A three-dimensional circulation model of the Chesapeake Bay is used to validate a simple data assimilation scheme, using high-resolution salinity data acquired from a ship-towed undulating vehicle (a Scanfish). The simulation period spans the entire year of 1995 during which the high-resolution Scanfish data were available in July and October, lasting a few days each. Since Scanfish data were irregularly distributed in time and space, only salinity fields are nudged in the model for simplicity. Model improvements through data assimilation are evaluated from a pair of experiments: one with data assimilation and one without. Data from scattered Chesapeake Bay ...


Evidence Of Countergradient Variation In The Growth Of An Intertidal Snail In Response To Water Velocity, Gc Trussell Jan 2002

Evidence Of Countergradient Variation In The Growth Of An Intertidal Snail In Response To Water Velocity, Gc Trussell

VIMS Articles

Growth rates in rocky intertidal snails can vary considerably across wave exposure gradients, and have both plastic and genetic bases. However, little is known regarding whether genetic and environmental influences on variation in growth act in the same (cogradient) or in an opposing (countergradient) direction. Determining how genetic and environmental influences on growth covary with one another may improve our understanding of how habitat-specific variation in growth emerges. This study utilized laboratory flumes to examine the effects of high and low water velocities on the growth of intertidal snails Littorina obtusata from a wave-exposed and a sheltered shore. Both flow ...